refactor multiple implementations of W3C trace context building into a dedicated helper

Author: na-ji

dd-java-agent/instrumentation/jdbc/src/main/java/datadog/trace/instrumentation/jdbc/JDBCDecorator.java

@@ -8,8 +8,8 @@
 import static datadog.trace.bootstrap.instrumentation.api.Tags.*;
 
 import datadog.trace.api.Config;
-import datadog.trace.api.DDSpanId;
 import datadog.trace.api.DDTraceId;
+import datadog.trace.api.W3CTraceParent;
 import datadog.trace.api.naming.SpanNaming;
 import datadog.trace.api.telemetry.LogCollector;
 import datadog.trace.bootstrap.ContextStore;
@@ -257,16 +257,6 @@ private AgentSpan withQueryInfo(AgentSpan span, DBQueryInfo info, CharSequence c
     return span.setTag(Tags.COMPONENT, component);
   }
 
-  public String traceParent(AgentSpan span, int samplingPriority) {
-    StringBuilder sb = new StringBuilder(55);
-    sb.append("00-");
-    sb.append(span.getTraceId().toHexString());
-    sb.append('-');
-    sb.append(DDSpanId.toHexStringPadded(span.getSpanId()));
-    sb.append(samplingPriority > 0 ? "-01" : "-00");
-    return sb.toString();
-  }
-
   public boolean isOracle(final DBInfo dbInfo) {
     return "oracle".equals(dbInfo.getType());
   }
@@ -294,7 +284,9 @@ public void setAction(AgentSpan span, Connection connection) {
       if (priority == null) {
         return;
       }
-      final String traceContext = DD_INSTRUMENTATION_PREFIX + DECORATE.traceParent(span, priority);
+      final String traceContext =
+          DD_INSTRUMENTATION_PREFIX
+              + W3CTraceParent.build(span.getTraceId(), span.getSpanId(), priority);
 
       connection.setClientInfo("OCSID.ACTION", traceContext);
 
@@ -380,7 +372,8 @@ public void setApplicationName(AgentSpan span, Connection connection) {
       if (priority == null) {
         return;
       }
-      final String traceParent = DECORATE.traceParent(span, priority);
+      final String traceParent =
+          W3CTraceParent.build(span.getTraceId(), span.getSpanId(), priority);
       final String traceContext = "_DD_" + traceParent;
 
       connection.setClientInfo("ApplicationName", traceContext);

dd-java-agent/instrumentation/jdbc/src/main/java/datadog/trace/instrumentation/jdbc/StatementInstrumentation.java

@@ -17,6 +17,7 @@
 import datadog.appsec.api.blocking.BlockingException;
 import datadog.trace.agent.tooling.Instrumenter;
 import datadog.trace.agent.tooling.InstrumenterModule;
+import datadog.trace.api.W3CTraceParent;
 import datadog.trace.bootstrap.CallDepthThreadLocalMap;
 import datadog.trace.bootstrap.InstrumentationContext;
 import datadog.trace.bootstrap.instrumentation.api.AgentScope;
@@ -119,7 +120,7 @@ public static AgentScope onEnter(
             Integer priority = span.forceSamplingDecision();
             if (priority != null) {
               if (!isSqlServer) {
-                traceParent = DECORATE.traceParent(span, priority);
+                traceParent = W3CTraceParent.build(span.getTraceId(), span.getSpanId(), priority);
               }
               // set the dbm trace injected tag on the span
               span.setTag(DBM_TRACE_INJECTED, true);

dd-java-agent/instrumentation/mongo/common/src/main/java/datadog/trace/instrumentation/mongo/MongoCommentInjector.java

@@ -4,7 +4,7 @@
 import static datadog.trace.bootstrap.instrumentation.api.InstrumentationTags.DBM_TRACE_INJECTED;
 
 import datadog.trace.api.Config;
-import datadog.trace.api.DDSpanId;
+import datadog.trace.api.W3CTraceParent;
 import datadog.trace.bootstrap.instrumentation.api.AgentSpan;
 import datadog.trace.bootstrap.instrumentation.dbm.SharedDBCommenter;
 import org.bson.BsonArray;
@@ -75,7 +75,8 @@ public static String buildComment(AgentSpan dbSpan, String hostname, String dbNa
     String dbService = dbSpan.getServiceName();
     String traceParent =
         Config.get().getDbmPropagationMode().equals(DBM_PROPAGATION_MODE_FULL)
-            ? buildTraceParent(dbSpan)
+            ? W3CTraceParent.build(
+                dbSpan.getTraceId(), dbSpan.getSpanId(), dbSpan.context().getSamplingPriority())
             : null;
 
     // Use shared comment builder directly
@@ -112,13 +113,4 @@ private static BsonValue mergeComment(BsonValue existingComment, String dbmComme
     // Incompatible type, preserve existing comment unchanged
     return existingComment;
   }
-
-  static String buildTraceParent(AgentSpan span) {
-    // W3C traceparent format: version-traceId-spanId-flags
-    return "00-" // version
-        + span.getTraceId().toHexString() // traceId
-        + '-'
-        + DDSpanId.toHexStringPadded(span.getSpanId()) // spanId
-        + (span.context().getSamplingPriority() > 0 ? "-01" : "-00");
-  }
 }

dd-java-agent/instrumentation/mongo/common/src/test/groovy/MongoCommentInjectorTest.groovy

@@ -1,6 +1,5 @@
 import datadog.trace.agent.test.InstrumentationSpecification
 import datadog.trace.api.config.TraceInstrumentationConfig
-import datadog.trace.api.sampling.PrioritySampling
 import datadog.trace.instrumentation.mongo.MongoCommentInjector
 import org.bson.BsonDocument
 import org.bson.BsonString
@@ -18,38 +17,6 @@ abstract class BaseMongoCommentInjectorTest extends InstrumentationSpecification
 }
 
 class MongoCommentInjectorTest extends BaseMongoCommentInjectorTest {
-  def "buildTraceParent with sampled flag (SAMPLER_KEEP)"() {
-    setup:
-    def span = TEST_TRACER.buildSpan("test-op").start()
-    span.setSamplingPriority(PrioritySampling.SAMPLER_KEEP, 0)
-
-    when:
-    String traceParent = MongoCommentInjector.buildTraceParent(span)
-
-    then:
-    traceParent != null
-    traceParent ==~ /00-[0-9a-f]{32}-[0-9a-f]{16}-01/
-
-    cleanup:
-    span?.finish()
-  }
-
-  def "buildTraceParent with not sampled flag (SAMPLER_DROP)"() {
-    setup:
-    def span = TEST_TRACER.buildSpan("test-op").start()
-    span.setSamplingPriority(PrioritySampling.SAMPLER_DROP, 0)
-
-    when:
-    String traceParent = MongoCommentInjector.buildTraceParent(span)
-
-    then:
-    traceParent != null
-    traceParent ==~ /00-[0-9a-f]{32}-[0-9a-f]{16}-00/
-
-    cleanup:
-    span?.finish()
-  }
-
   def "injectComment returns null when event is null"() {
     when:
     BsonDocument result = MongoCommentInjector.injectComment("test-comment", null)

dd-trace-api/src/main/java/datadog/trace/api/W3CTraceParent.java

@@ -0,0 +1,29 @@
+package datadog.trace.api;
+
+/**
+ * Utility class for building W3C traceparent headers.
+ *
+ * @see <a href="https://www.w3.org/TR/trace-context/#traceparent-header">W3C Trace Context</a>
+ */
+public final class W3CTraceParent {
+
+  private W3CTraceParent() {}
+
+  /**
+   * Builds a W3C traceparent header value from the given trace context components.
+   *
+   * <p>Format: {@code <version>-<traceId>-<spanId>-<flags>}
+   *
+   * @param traceId the trace id
+   * @param spanId the span id
+   * @param samplingPriority the sampling priority (positive values result in sampled flag set)
+   * @return the W3C traceparent header value
+   */
+  public static String build(DDTraceId traceId, long spanId, int samplingPriority) {
+    return "00-"
+        + traceId.toHexString()
+        + '-'
+        + DDSpanId.toHexStringPadded(spanId)
+        + (samplingPriority > 0 ? "-01" : "-00");
+  }
+}

dd-trace-api/src/test/groovy/datadog/trace/api/W3CTraceParentTest.groovy

@@ -0,0 +1,32 @@
+package datadog.trace.api
+
+import datadog.trace.test.util.DDSpecification
+
+class W3CTraceParentTest extends DDSpecification {
+
+  def "build produces correct format with samplingPriority=#samplingPriority"() {
+    when:
+    def result = W3CTraceParent.build(traceId, spanId, samplingPriority)
+
+    then:
+    result == expected
+
+    where:
+    traceId                                               | spanId              | samplingPriority | expected
+    DDTraceId.from(1)                                     | 2                   | 1                | "00-00000000000000000000000000000001-0000000000000002-01"
+    DDTraceId.from(1)                                     | 2                   | 0                | "00-00000000000000000000000000000001-0000000000000002-00"
+    DDTraceId.from(1)                                     | 2                   | -1               | "00-00000000000000000000000000000001-0000000000000002-00"
+    DDTraceId.from(1)                                     | 2                   | 2                | "00-00000000000000000000000000000001-0000000000000002-01"
+    DDTraceId.fromHex("0af7651916cd43dd8448eb211c80319c") | 0x00f067aa0ba902b7L | 1                | "00-0af7651916cd43dd8448eb211c80319c-00f067aa0ba902b7-01"
+    DDTraceId.from(Long.MAX_VALUE)                        | Long.MAX_VALUE      | 1                | "00-00000000000000007fffffffffffffff-7fffffffffffffff-01"
+  }
+
+  def "build matches W3C traceparent format"() {
+    when:
+    def result = W3CTraceParent.build(DDTraceId.from(123456789L), 987654321L, 1)
+
+    then:
+    // W3C format: version-traceId(32 hex)-spanId(16 hex)-flags(2 hex)
+    result ==~ /00-[0-9a-f]{32}-[0-9a-f]{16}-(00|01)/
+  }
+}

dd-trace-core/src/main/java/datadog/trace/core/propagation/W3CHttpCodec.java

@@ -16,6 +16,7 @@
 import datadog.trace.api.DDTraceId;
 import datadog.trace.api.TraceConfig;
 import datadog.trace.api.TracePropagationStyle;
+import datadog.trace.api.W3CTraceParent;
 import datadog.trace.api.internal.util.LongStringUtils;
 import datadog.trace.api.sampling.PrioritySampling;
 import datadog.trace.api.sampling.SamplingMechanism;
@@ -70,13 +71,10 @@ public <C> void inject(
     }
 
     private <C> void injectTraceParent(DDSpanContext context, C carrier, CarrierSetter<C> setter) {
-      StringBuilder sb = new StringBuilder(TRACE_PARENT_LENGTH);
-      sb.append("00-");
-      sb.append(context.getTraceId().toHexString());
-      sb.append('-');
-      sb.append(DDSpanId.toHexStringPadded(context.getSpanId()));
-      sb.append(context.getSamplingPriority() > 0 ? "-01" : "-00");
-      setter.set(carrier, TRACE_PARENT_KEY, sb.toString());
+      String traceparent =
+          W3CTraceParent.build(
+              context.getTraceId(), context.getSpanId(), context.getSamplingPriority());
+      setter.set(carrier, TRACE_PARENT_KEY, traceparent);
     }
 
     private <C> void injectTraceState(DDSpanContext context, C carrier, CarrierSetter<C> setter) {